The broad goal of this proposed project is to address questions about the nature of morbidity and mortality and their interrelationships using a large scale medfly model system. The proposed project will help frame basic questions about the dynamics of mortality, will serve as a model experimental system around which research on aging and mortality for other non-humans can be patterned and will contribute to knowledge of the biology of mortality and morbidity by gathering, analyzing and publishing data using large fruit fly cohorts raised under controlled conditions. There are four specific aims of prime interest to this program project on oldest-old mortality. 1. To determine the relationship between the age-specific schedules of mortality and morbidity in a minimum of once million medflies of both sexes. This relationship will be examined using both optimal and suboptimal environmental conditions to produce both high and low mortality rates. These results will test the hypothesis that morbidity rates decrease with increases in life expectancy and will provide the first detailed set of biological data on morbidity incidence and prevalence rates in a nonhuman species. 2. To measures and analyze age-specific mortality and reproductive traits of subsamples in the surviving 0.1% of both sexes starting with cohorts totaling 100 million medflies. This will provide a test of the hypotheses that mortality rates of medflies at the most advance ages remain low and that oldest old flies retain reproductive capabilities using a base population two orders of magnitude larger than previously examined. 3. To determine morbidity and mortality sex differentials over the life course of medflies. Specific questions include whether the gender gap increases or decreases with increasing life expectancies in medfly cohorts and whether the prevalence of morbidity is the same between males and females at low and high life expectancies. 4. To assess sex- and age-specific mortality rates in large cohorts (1 million flies) of two tephritid fruit fly species related to the medfly-- the Mexican fruit fly, Anastrepha ludens and the West Indian fruit fly, A. obliqua. Both species are mass-reared at the medfly rearing facility in Tapachula, Mexico and thus readily available in large numbers. The results of these trials will test hypothesis that slowing of mortality rates at advance ages is not unique to the medfly of Drosophila.